Problem: How many significant figures does $06.4540$ have?
Answer: Identify the non-zero digits and any zeros between them. These are all significant. $0{6.454}0$ Leading zeros are not significant. $\color{orange}{0}{6.454}0$ Since there is a decimal, trailing zeros are significant. $\color{orange}{0}{6.4540}$ Counting all the significant digits gives us 5.